This application claims all benefits accruing under 35 U.S.C xc2xa7119 from the Japanese Patent Application No. 10-272271, filed Sep. 25, 1998 and the Japanese Patent Application No. 11-240524, filed Aug. 26, 1999.
1. Field of the Invention
The present invention relates to a communication system which voice-code-compresses and transmits a voice signal from a voice terminal apparatus of a telephone terminal apparatus or a private branch exchange (hereinafter referred to as PBX) or the like, and particularly to a DTMF signal transmission method and communication apparatus for accurately transmitting a dual tone multi-frequency (hereinafter referred to as DTMF) signal including a push button (hereinafter referred to as PB) signal.
2. Description of the Related Art
Up to now, a communication system which voice-code-compresses and transmits a voice signal to the opposite side by means of a communication apparatus such as a multiplexer and the like has also voice-code-compressed and transmitted a DTMF signal such as a PB signal and the like sent from a telephone terminal apparatus as well as an ordinary voice signal to the opposite communication apparatus. That is to say, a communication apparatus at the transmission side voice-code-compresses and transmits as an ordinary voice signal a DTMF signal without paying a particular attention, and on the other hand, a communication apparatus at the reception side voice-code-expands and restores the received voice-code-compressed signal to a voice signal (DTMF signal) and sends it to a voice terminal apparatus of a PBX or the like, and the voice terminal apparatus judges and recognizes the code of the DTMF signal and performs a specified operation.
Like the above-mentioned prior art, however, in case of compressing and expanding a DTMF signal as one of voice signals, there has been a problem that a DTMF signal (voice signal) expanded by a communication apparatus at the reception side is out of a reception rule and is sometimes not recognized as a DTMF signal by a voice terminal apparatus side of a PBX and the like.
And in case of transmitting a DTMF signal, there has been a problem that since a communication apparatus side which has received a DTMF signal needs a judgement time for judging the DTMF signal and the DTMF signal is transmitted to the opposite voice terminal apparatus as a voice signal during the judgement time, a DTMF signal restoring side obtains a DTMF sound by expanding a voice-code-compressed DTMF signal and then restores a DTMF signal obtained by decoding a DTMF signal and thus the DTMF sound obtained by expanding a voice-code-compressed signal sometimes comes to be out of a reception rule for a DTMF signal and sometimes is not recognized as a DTMF signal by a voice terminal apparatus side of a PBX or the like.
An object of the invention is to provide a DTMF signal transmission method and communication apparatus capable of judging/recognizing a DTMF signal without error by means of a communication apparatus at the reception side (voice terminal apparatus) even in case of transmitting the DTMF signal by means of a communication apparatus for performing a voice code compression.
The present invention is characterized by a communication apparatus connected to a voice terminal apparatus and a communication channel, said communication apparatus comprising;
a voice code compressing means for generating voice information by code-compressing a voice signal from said voice terminal apparatus and sending out this voice information to said communication channel,
a voice code expanding means for generating a voice signal by code-expanding compressed voice information from said communication channel and sending out this voice signal to said voice terminal apparatus,
a detecting means for detecting whether or not a DTMF signal is contained in a voice signal from said voice terminal apparatus,
a DTMF coding means for, when said detecting means has detected a DTMF signal, generating DTMF information by coding the said DTMF signal into a specified form and sending out this information to said communication channel,
a DTMF decoding means for decoding coded DTMF information from said communication channel, and
a DTMF generating means for generating a DTMF signal on the basis of the content decoded by said DTMF decoding means and sending out this DTMF signal to said voice terminal apparatus.
And the present invention is characterized by a communication system comprising a transmission side voice terminal apparatus, a transmission side communication apparatus for connecting said transmission side voice terminal apparatus, a reception side voice terminal apparatus and a reception side communication apparatus for connecting said reception side voice terminal apparatus in which communication system said transmission side communication apparatus and said reception side communication apparatus are connected through a communication channel to each other, wherein;
said transmission side communication apparatus is provided with;
a voice code compressing means for generating voice information by code-compressing a voice signal from said transmission side voice terminal apparatus and sending out this voice information to said communication channel,
a detecting means for detecting whether or not a DTMF signal is contained in a voice signal from said transmission side voice terminal apparatus, and
a DTMF coding means for, when said detecting means has detected a DTMF signal, generating DTMF information by coding the said DTMF signal into a specified form and sending out this DTMF information to said communication channel, and
said reception side communication apparatus is provided with;
a voice code expanding means for generating a voice signal by code-expanding compressed voice information from said communication channel and sending out this voice signal to said reception side voice terminal apparatus,
a DTMF decoding means for decoding coded DTMF information from said communication channel, and
a DTMF generating means for generating a DTMF signal on the basis of the content decoded by said DTMF decoding means and sending out this DTMF signal to said reception side voice terminal apparatus.